It is proposed to use ionizing radiation to graft certain monomers to the plastic parts of extracorporeal blood circulation equipment such as membrane oxygenators. Each monomer grafted will bear a chemical grouping capable of reacting with and linking to heparin. The grafted plastic parts will then be treated with heparin, resulting in the chemical bonding of heparin to the plastic parts, and rendering the plastic parts nonthrombogenic. A detailed study of the results should yield a better understanding of the heparin antithrombogenic effect.